1. Field of Invention
This invention relates in general to levels that are used in the construction trades and in particular to levels which are used primarily in a vertical position, and are of an adjustable length.
2. Prior Art
In the construction trades, the framed walls of a structure, both interior and exterior, are composed of vertical members commonly called studs, and horizontal or sometimes sloped members commonly called plates. Typically, a wall will have an upper plate and a lower plate with vertically positioned studs fastened between the two plates. In order for the stud wall to be perfectly “plumb”, the upper plate must be directly over the lower plate, that is the plates must be in the same plane. The most accurate procedure for the measuring and adjusting the plumbness of the wall is to place a level against the upper and lower plates, adjusting the wall until the level indicates that the wall is perfectly vertical, and then securing the wall in that position. However, studs are usually longer than a conventional level, causing the stud wall to be taller than the length of a conventional level. Therefore, a conventional level is too short to reach from the bottom plate to the top plate. This shortcoming necessitates that the level be positioned against one of the studs of the erect wall, adjusting the wall until the level indicates plumbness of that stud, and then securing the wall in that position. All is fine if the chosen stud is perfectly straight. To those skilled and experienced in the construction trades, it is common knowledge that studs, whether they are of metal or wood, but especially those made of wood, are seldom perfectly straight. The plumbness of the wall then becomes dependent upon the straightness of the studs and placement of the level on the crooked stud.
The present invention provides the solution to the problem of plumbing a stud wall that is composed of crooked studs, by providing a device that can be adjusted to a sufficient length to quickly and accurately span the distance between the upper plate to the lower plate.
In the prior art, various types of adjustable levels are known. For example, U.S. Pat. No. 4,130,943 discloses an adjustable level which is extendible in 6-inch increments. U.S. Pat. No. 4,152,838 discloses a level with a sliding scale. U.S. Pat. No. 4,435,908 discloses an adjustable level with offset members to plumb warped studs. U.S. Pat. No. 4,607,437 discloses an adjustable level with extension legs that are extendible perpendicular to the longitudinal axis of the level. U.S. Pat. No. 4,733,475 discloses an extension level with a spring-loaded member that allows the level to be retained in a wall opening. U.S. Pat. No. 4,928,395 discloses an extensible level in which the extenders are locked in longitudinal tracks on the level. U.S. Pat. No. 5,155,917 discloses a collapsible pocket level. U.S. Pat. No. 5,249,365 discloses a level with telescoping extenders. U.S. Pat. No. 5,617,641 discloses an adjustable length level with no provision for locking the ends in place. However all of the prior art levels suffer from various drawbacks. For example, the level in U.S. Pat. No. 4,130,943 is adjustable only in lengths of fixed increments. If the user wants a level of a length somewhere in between the fixed increments, the level is incapable of obtaining such a length. U.S. Pat. No. 5,617,641 discloses an adjustable length level with no provision for locking the ends pieces in place. U.S. Pat. No. 6,915,585 discloses a spirit level which can extend in length, but has a very limited range of less than twice its original length.